Impact dampers of the generic type have been disclosed for instance by DE 21 49 759 C3. In principle, these known dampers are formed as conventional hydraulic dampers, i.e. they have a cylindrical housing closed at one end, in which a damping piston with damping channels is arranged for axial displacement and is secured to one end of a piston rod exiting in sealed manner at one end of the cylindrical housing. The compressible solids utilized are such materials as they are known from U.S. Pat. No. 3,053,526 or as they are commercially available under the trade name "Silastic" of Dow-Corning Corporation, U.S.A. When the piston rod enters, their volume is displaced, i.e. the compressible solid is compressed by the penetrating volume of the piston rod. Simultaneously the solid is pressed through the damping channels of the piston, as a result of which extraordinary damping occurs. The damping channels can also be formed by an annular gap between the piston and the internal wall of the housing. The compression of the solid simultaneously pretensions the latter, so that when correspondingly unloaded the piston rod is again pushed out of the housing. Such impact dampers are widely used in practice where they have proved quite a success, in particular when arranged between the bumper bar and the frame of a vehicle. In practice, they can as a rule absorb a crash of the vehicle on an obstacle up to a spaed of about 8 kmh in reversible manner, i.e. without any deformations and damages being caused to the vehicle.
German patent 34 19 165 discloses an impact damper having on the one hand a gas spring and on the other hand a hydraulic damper arranged in a cylindrical housing, in both of which a damping piston with a tubular piston rod is arranged. Hydraulic damping takes place through a throttle stationarily arranged in the housing. The hydraulic crash damping and the damping through the gas spring are reversible. So as to achieve an additional absorptive effect after termination of the full working stroke of the piston, the latter's tubular piston rod is provided with a predetermined buckling point, so that when a predetermined energy to be damped is exceeded, the tubular piston rod is destroyed absorbing corresponding deformation energy. This impact damper is comparatively expensive and long.